MAJOR IDENTITY DETERMINANTS IN THE AUGMENTED-D-HELIX OF TRNA(GLU) FROM ESCHERICHIA-COLI

By a kinetic analysis of 59 variant transcripts of Escherichia coli tR NA(Glu) with glutamyl-tRNA synthetase (GluRS), the U11 . A24 base-pair , the U13 . G22 .. A46 base-triple, and the lack of residue 47 (Delta 47) were found to serve as major determinants for tRNA(Glu) identity. This is the first system for which major identity determinants are rep orted to be clustered in the ''augmented D helix'', consisting of the D stem with some neighboring residues and the variable loop. Other ide ntity determinants are U34, U35, C36 and A37 in the anticodon loop, an d G1 . C72 and U2 . A71 in the acceptor stem. Phosphate-group protecti on by GluRS from ethylnitrosourea was observed most strongly for the m inor groove side of D-stem helix, indicating that GluRS tightly binds to the D stem for recognition, on the minor groove side, of the potent identity-determinant groups of the U11 . A24 and U13 . G22 base-pairs . A46 is not involved in direct recognition by GluRS; the U13 . G22 .. A46 base-triple is required probably for formation of the structural features that are recognized by GluRS. In this context, the essential role of Characteristic Delta 47 in tRNA(Glu) identity may be to mainta in the U13 . G22 .. A46 base-triple. (C) 1996 Academic Press Limited